A lightweight DSD-UNet-based method for clustered litchi segmentation.

Automated litchi harvesting demands clustered fruit segmentation with both high accuracy and real-time performance, yet high computational complexity and parameter redundancy pose critical bottlenecks for practical deployment. To tackle these challenges, we propose a lightweight DSD-UNet method for fast and high-precision segmentation of litchi clusters. The DSD-UNet incorporates depthwise separable convolutions to replace traditional convolutional structures, significantly reducing parameters and computational complexity. To further enhance the model's performance, we introduce a dual cross-attention mechanism into the skip connections,which integrates spatial and channel attention to adaptively strengthen the representation of target regions in feature maps and improve sensitivity to slender stem features. Additionally, we develop a composite loss function (BL-Loss), combining binary cross-entropy with level-set loss, and optimize it using a staged training strategy to alleviate within-foreground pixel imbalance and preserve the boundary continuity of slender fruit-stem connections. Experimental results under varying illumination conditions demonstrate that DSD-UNet achieves a mean Intersection over Union (